Separation of higher fatty acids



Patented June 15, 1948 SEPARATION OF HIGHER FATTY ACIDS.

Edwin W. Colt, Evanston, 111., assignor to Armour and Company, Chicago, 111., a corporation of No Drawing. Application December 20, 1943,

Serial N0. 514,969

16 Claims. (Cl. 260-419) This invention relates to treatment of fatty acid mixtures to separate the same into portions containing differing kinds or proportions of the component acids of the mixture. Mor particularly the invention relates to processes wherein a fatty acid mixture is subjected to crystallization to obtain solid and liquid phases and wherein the mixture is pretreated to facilitate the separation of the acids in the crystallizing procedure.

The unsaturated fatty acids, such as oleic and linoleic acids, are in great commercial demand. They are used in the manufacture of paints, varnishes and other coating compositions and have many other important uses.- They are used in the manufacture of a vast number of chemical compositions. The saturated fatty acids such as stearic and palmitic acids are also in commercial demand but usually have different purposes. As a general matter, the saturated fatty acids are undesirable for purposes to which the unsaturated fatty acids are best suited and the unsaturated fatty acids are undesirable or less desirable for the purposes to which the satur'atedfatty acids are best suited.

The common commercial sources of fatty acids are the naturally occurring fats and oils, the fatty acids being obtained by hydrolysis of the fats and oils which results in the production of fatty acid mixtures and glycerin. These mixtures, which we may call natural fatty acid mixtures, usually contain at least one unsaturated fatty acid in a substantial amount, and two or more saturated fatty acids in varying amounts and proportions.

In the preparation of paints, enamels and the like, the saturated acid content of the natural fatty acid mixtures are a substantial detriment in that they greatly reduce the time required for drying and deleteriously affect the general character of the film. Furthermore, by their inclusion with acids used in the paint field, for example, they are lost to other uses for which they are well suited. The commercial need for efiicient processes for separating unsaturated acids from the saturated acids with which they are found, has long been recognized.

A process which has been used for many years and which is widely used: in commercial practice today involves the pressing of acids obtained from tallow, lard, garbage grease, and the like,

to produce what is known in the trade as commercial stearic acid and red oil or commercial oleic acid. The commercial stearic acid is a mixture principally of palmitic and stearic acids, which, as a practical matter, has always con- 2 I tained a certain amount of unsaturated acids. The commercial red oil is a mixture of unsaturated acids, which, as a practical matter, has always contained a certain amount of saturated acids.

By this process long practiced by the art the fats are split by Twitchelizing or other well known process, and the natural acid mixture so obtained is chilled to -about 40 F., the resulting cakes wrapped in fabricand pressed in mechanical presses. Some of the unsaturated acids are removed in this way but large quantities are retained in the cake. The pressing operation is repeated at elevated temperature and usually the cake is pressed yet a third time, but the saturated acids are still not obtained in a high degree of purity.

I have discovered a process by which the fatty acid mixtures may be separated into a solid portion containing saturated acids and a liquid portion containing unsaturated acids, the separation being very effective especially as to certain natural acid mixtures, the improved process being quite simple and economical in operation.

Briefly stated, my process includes the fractional crystallization of a fatty acid mixture which has been pretreated to facilitate the crystallizing procedure. The pretreatment of the acid mixture includes subjecting the mixture to a fractional distillation step to remove at least a. part of a saturated fatty acid of shorter chain length which has been found to adversely affect the solubility characteristics of a longer chain saturated fatty acid contained in the mixture. With the shorter chain saturated acid removed, the mixture containing saturated and unsaturated acids is subjected to fractional crystallization to obtain solid and liquid fractions, the solid fraction containing saturated acids and the liquid fraction containing unsaturated acids. The separation between the saturated and unsaturated acids is, by the improved method, much more sharp and eflicient than has been obtained by the commercial practices heretofore followed. As will be explained more fully later in this specification, I attribute this result to improved crystal formation due largely to the eflect of the pretreatment in removing objectionable solubility influences.

The improved process is applicable to any fatty acid mixture containing saturated and unsaturated fatty acid components in which one saturated fatty acid component is of shorter chain length than another saturated fatty acid component or the unsaturated fatty acid component.

tained by splitting or hydrolysis of the naturally occurring oils or fats of both animal and vegetable origin. Important animal sources are lard, tallow, brown grease and fleshing grease, and important sources of vegetable origin are soy bean, peanut, cottonseed and rapeseed oils.= Other vegetable sources are palm,'olive, com,- sunflower, tung, linseed and coconut oils. The marine oils such as whale, menhaden, sardine and herring oils are also good sources.-

The mixtures of acids recovered through hy I drolysis from such sources as those above men-' tioned are called natural fatty acid mixtures and the natural fatty acid mixtures of the specific oils are designated by reference to their source, for example, the acid mixture obtained by hydrolysis of lard is called lard fatty acid, and the acid mixture obtained by hydrolysis of soybean oil'is called soybean oil fatty acid, etc. The improved process has been found particularly valuable in connection with soybean oil, cottonseed oil and lard, and'the special advantage with respect to these acid mixtures is believed due, in part, to the particular proportions of the various fatty acids contained in these mixtures which makes them especially susceptible to improvement in crystallization. s

Soybean oil fatty acids, for example, contain approximately 6.5% palmitic acid (containing a chain of 16 carbon atoms), 4.5% stearic acid (18 carbons), 33% oleic acid (18 carbons), 52% linoleic acid (also '18 carbons); and tallow contains approximately 2% myristic acids (14 carbons) 30%palmitic acid, 21% stearic acid, 45% oleic acid and 2% linoleic acid. After subjecting such mixtures to fractional distillation to remove the palmitic acid or a substantial part of the palmitic acid, the remaining fraction when crystallized will give much more satisfactory separation between the linoleic and oleic acids on one hand and the saturated acids including stearic acid on the other hand,

The pretreatment of the fatty acid mixtures before the crystallizing step includes the distillation of the mixtures in such a way as to separate a low boiling fraction containing a concentration of the shorter chain saturated fatty acids and obtain an acid fraction containing saturated as well as unsaturated acids but containing substantially none, or at least a lesser quantity, of the low boiling short chain saturated fatty acids than are contained in the original mixture. The separation by fractional distillation is a separation substantially according to carbon chain length since the fatty acids have boiling points which vary approximately according to their chain lengths. Thus, a low boiling fraction will contain a concentration of the shorter chain acids. With a mixture of oleic, stearic and palmitic acids the low boiling fraction will contain a concentration of palmitic acid. When I describe a fraction or portion of the acid mixture as containing a concentration of some named acid I mean this fraction or portion contains a higher proportion of the named acid than is contained .in the original mixture which is subjected to treatment.

When referring to two fatty acids of different chain lengths I use the terms relatively long chain" and relatively short chain" to distinguish between these acids, and do not intend to describe the chain lengths of either acid except with reference to the other.

The apparatus and operating practices for carv This includes the natural fatty acid mixtures obrying out the fractional distillation of the acid mixtures is now well known and need not be set forth in detail. Those familiar with this art will understand how to vary the conditions and adjust the apparatus to obtain the desired fractions of diiierent boiling points, making allowances for the source orfiacid'compositmn of the step, to remove all or substantially all of the shorter chain length saturated acids, but some benefltswill be obtained in the crystallizing step where any part of the shorter chain acids are removed. Referring to particular acid mixtures, in the 'case of tallow, lard, palm, olive, cottonseed, corn, peanut, soybean, sunflower or linseed.

oil acids, it is advantageous to remove by fractional distillation a fraction containing a concentration ofpalmitic acid. In the case of coconut or palm kernel oil acids,,a fractlonmay be removed containing a concentration of caproic (6 carbons), caprylic, (8 carbons) and capric (10' carbons) acids; and, if desired, a further fraction may be removed, this further fraction containing a concentration of lauric and possibly myristic and palmitic acids, to obtain a resulting fraction containing concentrations of oleic, linoleic and stearic acids which is subjected to fractional crystallization. It will be observedthat the fraction removed, whether it be a first, second or other fraction, contains a concentration of a saturated fatty acid having a shorter carbon chain length than another saturated fatty acid which is desired to be separated from an unsaturated fatty acid, 1

It is to be expected that the fraction removed by distillation will usually contain some relatively long chain saturated acids as well as unsaturated fatty acids, but when the distillation is efliciently performed, the quantities of such other acids should be small.

Most of the natural fatty acid mixtures contain in excess of 10% of saturated acids, usually palmitic and stearic'aci and when a low boiling fraction is removed 1 cm such mixtures. this serves to reduce the low boiling saturated component of the mixture so as to markedly decrease the ratio of the relatively short chain saturated acids to the relatively long chain saturated acids which is the object of the pretreatment step. Thus it will be understood thatwhen natural oils or fats are hydrolyzed and the resulting'mixture fractionally distilled to reduce the saturated acids to less than 10%, the pretreatment step of my process is practiced.

It is preferable not only to reduce saturated acids to below 10% but to reduce the number of saturated fatty acids present. It is preferable to reduce the saturated fatty acids to but a single chain length. For example, where the mixture contains saturated acids of three difierent chain lengths it is beneficial to remove acids of the.

better will be the results "obtained in the crystallizing procedure. ,Preferably all but one ofthe saturated fatty acid components should be removed.

In the fractional distillation procedure three portions are usually obtained, a low boiling volatile portion containing a concentration of relatively short chain fatty acids, a bottoms'portion containing pitch andhrisaponifiable matter and a certain amount of the longest chain fatty acids, and a-higher boiling volatile portion containing a concentration of the relatively long chain fatty acids. It is this last mentioned fraction which is utilized in the crystallizing procedure of this invention. The fraction subjected to crystallizing may also contain some part of the pitch and unsaponifiable matter. Also the fraction to be crystallized may be subjected to further fractionation or treatment. It is preferable, however, to utilize the high boiling volatile fraction obtained as above described having a low boiling volatile fraction and the pitch excluded.

The fractional crystallization may proceed in various ways. The acid mixture treated as above set forth and containing both saturated and unsaturated fatty acids, may simply be cooled to a -temperature at which a partial crystallization occurs. For example, in the case of a soybean oil acid fraction containing about 0.4% palmitic acid, 6% stearic acid, and 93.6% unsaturated acids (oleic, linoleic and linolenic), the fraction may be cooled to about 65 F. The solid phase is then separated from the liquid phase'by filtering or any other suitable means.

By using the treated acid mixture the solid crystals obtained are well defined and a sharper separation is obtained than was ever possible using the crystallizing methods heretofore practiced, the solid phase containing a higherproportion of saturated acids and a lesser proportion of unsaturated acids and the liquid phase containing a higher proportion of unsaturated acids and a lesser proportion of saturated acids.

Though not in all cases necessary, the liquid portion obtained by the first crystallizing step may be further cooled to obtain a second solid fraction whichis separated from the liquid portion. This fraction obtained by the second crystallization may contain further quantities of saturated acids and will probably contain a greater proportion of unsaturated acids than does the first solid fraction. Any number of successive crystallizing steps may be used, and in this way it is possible also to separate the more highly unsaturated acids from the less highly unsaturated acids, for example, to separate linoleic acid from oleic acid. However, the improvement imparted through the use of the pretreatment step lies principally in the crystallization to separate the saturated from the unsaturated acids.

A more efficient way of carrying out the crystallizing procedure is to dissolve the pretreated fatty acid mixture in a suitable organic solvent such as acetone and then to cool the mixture while so dissolved to a temperature at which partial crystallization occurs. The solid phase is then separated from the liquid phase, and the solvents preferably recovered for reuse.

' I find that greatly improved results can be obtained using one of the following solvents:

acetone, methyl ethyl ketone, ethylor methyl alcohol, benzol, paraiiln hydrocarbons such as hexane, propane, butane, etc. Of these I find acetone to be one of the most suitable. Mixtures of these solvents may also be employed.

In carrying out the procedure using an added solvent, the treated acid mixture may be mixed with the solvent in a suitable mixing vat or chamber, the solvent being used in a proportion of the neighborhood of two to six or'more volumes of solvent to one volume of acids. The mixture of acids dissolved in the solvent may desirably be passed continuously through a heat exchange unit where it is partially cooled and then may be passed through a chilling unit where the temperature is reduced sufilciently to crystallize saturated acids contained therein. The temperature reduction necessary to produce this 'orystallization will vary substantially with the proportion of solvent to acids.

The chilled acids containing a solid phase may then be passed through a filter of a suitable type to remove the crystallized acids from the liquid acids. These separate portions may then be passed to suitable stills for the recovery of solvent for reuse in the process.

Instead of passing the liquid phase portion to the solvent recovery stills this portion may be passed through a further chilling unit where the temperature is reduced to the point at which the least unsaturated fatty acids will crystallize. This is advantageous, for example, where the acid fraction being crystallized contains both linoleic acid and oleic acid and it is desired to separate these acid-s. When the unsaturated acids are separated from each other by this further crystallization step it is preferable to add more solvent to the liquid phase mixture before the second chilling operation so that there is a greater proportion of solvent at this point than is contained in the mixture which was first chilled and filtered. After chilling to the lower temperature, the mixture containing the least unsaturated acid in solid phase may be passed through a filter and the solid portion removed. Each of the portions contained may be passed to stills where solvent is recovered for reuse.

Where a treated fatty acid mixture contains linoleic, oleic and stearic acids, by practicing the above procedure there may be obtained afirst solid fraction which contains a high concentration of stearic acid; a second solid fraction which contains a high concentration of oleic acid, and a. third fraction which contains a high concentration of linoleic acid.

As a more specific explanation of operations according to the inventionthe following specific examples are given:

Example I Soybean oil is hydrolyzed to recover a fatty acid mixture of iodine value, containing 11% saturated acids (about 6.5% palmitic and 4.5% stearic). This mixture is fractionally distilled to remove a low boiling portion and to obtain a fraction containing 6% saturated acids which includes about 5.0% stearic acid. This fraction is mixed with five times its weight of butane and the temperature lowered to about 25 F. to produce crystallization of the saturated acids. The liquid phase acids when separated have an iodine number of and contain less than 1% of saturated acids. The product has greatly improved characteristics when used in the preparation of alkyd resins and other coating compositions, and is satisfactory for such uses where the product heretofore obtained commercially from soybean oil is not satisfactory for these uses.

Example If alkyds made with fatty acid mixtures containing the normal saturated acids.

It will be understood that in any crystallizing procedure it is possible to remove larger solid portions and so obtain a resulting liquid phase portion which is more free from saturated acids. However, such an improvement in the unsaturated'portion is obtained at the expense of the purity of the saturated fraction and the yield of unsaturated acids obtained from a given amount rated portion having 2% saturated acids and a color as good as the distilled product of the previously described operation in a yield of 70.5% of the original cottonseed oil fatty acid mixture. whereas in the first operation with the pretreatment step omitted the yield is only 55.8%.

To take another comparison, 1000 parts of a natural soybean oil fatty acid mixture containing 70 parts (7%) of palmitic acid, 50 parts (5%) of stearic acid and 830 parts (88%) of unsaturated acids are fractionally crystallized in three stages to obtain a solid fraction amounting to '263 parts (26.3% of the original mixture) conof the original mixture. By the improved process I of this invention the separation between the saturated and unsaturated acids may be accomplished without sacrificing the yield or purity of either portion. In order to demonstrate this result I set forth the following description of parallel crystallizing operations, the first of which is performed omitting -the pretreatment step herein described and the second utilizing this step:

1000 parts of natural cottonseed oil fatty acid mixture containing 210 parts (21%) of palmitic acid, 20 parts (2%) of stearlc acid and 770 parts (77 of unsaturated acids, are fractionally crystallized in three stages to obtain a solid fraction amounting to 442 parts (44.2% of the original mixture) containing 201 parts (44.5%) of palmitic acid, 20 parts (4.5%) of stearic acid and 221 parts (50%) of unsaturated acids, and a liquid fraction amounting to 558 parts (55.8% of the original mixture) containing 9 parts (2%) of palmltic acid, a trace of stearic acid, and 549 parts (98%) of unsaturated acids. There is thus obtained a material with a 2% saturated acid content in a yield of 55.8%. If this material be straight distilled to remove non-volatile matter and to improve the color, the yield is 54.1%.

In the second operation the same material is employed as in the first operation just described. 1000 parts of this material is iractionally distilled to obtain a low boiling volatile fraction amounting to 220 parts (22% of the original mixture) containing 198 parts (90%) of palmitic acid, a trace of stearic acid and 22 parts (10%) of unsaturated acids, and a high boiling volatile fraction amounting to 730 parts (73% of the original mixture) containing 12 parts (1.6%) of palmitic acid, 20 parts (2.7%) of stearic acid and 698 parts (95.7%) unsaturated acids, and a pitch portion amounting to parts (5% of the original mixture). The high boiling volatile fraction so obtained is fractionally crystallized in one sta e and without the addition of foreign solvent to obtain a solid fraction amounting to 25 parts (2.5% of the original mixture) containing 4 parts (16%) of palmitic acid, 12 parts (48%) of stearic acid and 9 parts (36%) of unsaturated acids, and a liquid fraction in the amount of 705 parts (70.5% of the original mixture) containing 8 parts 1%) of palmitic acid, 8 parts (1%) of stearic acid and 689 parts (98%) of unsaturated acids. Thus with only .a single crystallizing stage there is obtained an unsatutaining 63 parts (24%) of palmitic acid, 43 parts (16%) of stearic acid and '157 parts (60%) of unsaturated acids, and a liquid fraction amounting to 731 parts (73.7% of the original mixture) containing 7 parts (1%) 01' palmitic acid, 7 parts (1%) of stearic acid and 723 parts (98%) of unsaturated acids. There is thus obtained a material with a-2% saturated acid content in a yield of 73.7%. If this material be straight distilled to remove non-volatile matter and to improve the color, the yield is 71.5%.

In a second operation using the same soybean acid mixture, 1000 parts of this material is fractionally distilled to obtain a low boiling volatile fraction amounting to 90 parts (9% of the original mixture) containing 66 parts (73%) of palmitic acid, 2 parts (2%) of stearic acid and 22 parts (25%) of unsaturatedacids, and a high boiling fraction amounting to 860 parts (86% of the original mixture) containing. 4 parts (0.4%) of palmitic acid, 48 parts (5.6%) of stearic acid and 808 parts (94%) of unsaturated acids, and a pitch portion amounting to 50 parts (5% of the original mixture) The high boiling volatile fraction so obtained is iractionally crystallized in one stage without the addition of foreign solvent to obtain a solid traction amounting to 56 parts (6.5% of the high boiling fraction) containing 4 parts (7%) of palmitic acid, 33 parts (59%) of stearic acid and 19 parts (34%) of unsaturated acids, and a liquid fraction amounting to 804 parts (93% of the high boiling fraction) containing' no detectable palmitic acid, 15 parts (2%) of stearic acid and 789 parts (98%) of unsaturated acids. Thus with only a single crystallizing stage there is obtained an unsaturated soybean acid product having 2% saturated acids and a color as good as the distilled product of the previously described operation involving soybean oil acids in a yield of 80.4% of the original soybean acid mixture, whereas by the operation omitting the pretreatment step a yield of only 73.7% is obtained.

Though the reasons for the improved results obtained in the crystallizing procedure according to this invention are not completely understood. at least a partial explanation may be found in the altered solubility characteristics of the saturated acids which is solidified in the crystallizing step.

be more soluble and tocrystall'iae at a lower temperature byreason of its association with the molecules of the shorter chain fatty acids. Such influence is not present between the shorter chain acids and the unsaturated acids or between unsaturated fatty acids of different chain lengths or if present at all is not present nearly to the same extent that it exists between the saturated acids.

It, therefore, appears that where saturated and unsaturated acids are separated by crystallizing and where saturated acids of two or more chain lengths are present, the shorter chain length acids tend to raise the solubility of the longer chain acids to a point more nearly approaching the solubility of the unsaturated fatty acids.

.This operates to narrow the differential between the temperature at which the saturated acids crystallize and the temperature at which the unsaturated acids crystallize, making separation difficult and overlapping prevalent with the consequent impurity of the separate portions obtained. I In the pretreatment step of the present invention the relatively short chain fattyacids or a substantial part thereof are removed through fractional distillation, and this has the effect of substantially avoiding the tendency to raise the solubility of the longer chain saturated fatty acids. With this tendency avoided there is a greater differential between the temperatures at which the unsaturated acids crystallize and the temperature at which the longer. chain saturated fatty acids crystallize, and separation by crystallization is cleaner and sharper, resulting in purer fractionsand easier operation.

The foregoing detailed description has been given for purposes of explanation only and specific practices have been outlined without any intention of limiting the invention to the steps and conditions set forth. Many modified procedures may be practiced, and many changes may be made,-all within the spirit of the invention.

This application is a continuation in part of my co-pending application Serial No. 358,563 filed September 26, 1940, entitled "Treating fatty acidcontaining stock subsequently abandoned."

What I claim, and desire to procure in Letters Patient is:

1. A process for treating a fatty acid mixture containing an unsaturated higher fatty acid, a relatively long carbon chain saturated higher fatty acid and a, relatively short carbon chain saturated higher fatty acid to separate saturated from unsaturated acids, comprising fractionally distilling said mixture to remove a fraction containing a concentration of said relatively short chain saturated fatty acid and to obtain a fraction containing said unsaturated fatty acid and said relatively long chain saturated fatty acid, said relatively long chain saturated fatty acid being less soluble when in said fraction than when in said mixture. and fractionally crystallizing said fraction to obtain a solid fraction containing a concentrationof said relatively long chain saturatedfatty acid and a liquid fraction containing a concentration of said unsaturate fatty acid.

2. A process for treating a fatty acid mixture containing an unsaturated higher fatty acid,

stearic acid and palmitic acid to separate said acida,eomprisifig fractionally distilling said mixture to remove a fraction containing a concentration of palmitic acid, and fractionally crystallizing at least a portion of the remainder of said mixture containingsaid unsaturated acid and stearic acid and in which said stearic acid is less soluble than in said mixture to obtain a solid fraction containing a concentration of stearic acid and a liquid fraction containing a concentration of said unsaturated fatty acid.

3. A process for treating a fatty acid mixture containing oleic, stearic and palmitic acids to separate the oleic from the stearic and palmitic acids, comprising fractionaily distilling said mixture to remove a fraction containing a concentration of palmitic acid and to obtain a fraction containing oleic and stearic acids, the stearic acid being less soluble when in said fraction than when in said mixture, and fractionally crystallizing said fraction to obtain a solid fraction containing a concentration of stearic acid and a liquid fraction containing a. concentration of oleic acid.

4. A process as called for in claim 1 in which said fatty acid mixture is soy bean oil fatty acid mixture. i

5. A process as called for in claim 1 in which said fatty acid mixture is cottonseed oil fatty urated higher fatty acid having shorter carbon chain than said first-mentioned, saturated fatty acid, comprising fractionally distilling said mixture to remove a fraction containing a concentration of said second-mentioned saturated fatty acid and to obtain a fraction containing said unsaturated fatty acid and said second-mentioned saturated fatty acid, said first-mentioned saturated fatty acid being lesssoluble when in said fraction than when in said mixture, and fractionally crystallizing said fraction to obtain a solidfraction containing a concentration of said first-mentioned saturated fatty acid and a liquid fraction containing a concentration of said unsaturated fatty acid.

8. A process for treating a fatty acid mixture containing an unsaturated higher fatty acid, a relatively long carbon chain saturated higher fatty acid, and a relatively short carbon chain saturated higher fatty acid to separate saturated from unsaturated acids, comprising fractionally distilling said mixture to recover a fraction containing said unsaturated fatty acid'and said relatively long chain fatty acid and containing a reduced proportion of'said'relatively short chain fatty acid, said relatively long chain fatty acid being more insoluble when in said fraction than when in said mixture, reducing the temperature of said fraction until at least a part of said rela- 11 tively long chain acid crystallizes, and separating the solid phase from the liquid phase.

9. A process for treating a fatty acid mixture containing an unsaturated higher fatty acid, a relatively long carbon chain saturated higher fatty acid and a relatively short carbon chain saturated higher fatty acid to separate saturated from unsaturated acids, comprising fractionally distilling said mixture to remove a fraction containing a concentration of said relatively short chain saturated fatty acid and to obtain a fraction containing said unsaturated fatty acid and said' relatively long chain saturated fatty acid,

- dissolving said last-mentioned fraction in a foreign organic solvent in which the fatty acids contained in said fraction are soluble, said relatively long chain saturated fatty acid being less soluble when in said fraction than when in said mixture. and fractionally crystallizing said fraction in said solvent to obtain a solid fraction containing a concentration of said relatively long chain saturated fatty acid.

10. A process as set forth in claim 9 wherein said solvent is acetone. a

11. In a. process for treating natural oils and fats containing unsaturated fatty acids and a plurality of saturated fatty acids, the steps of hydrolyzing the oils and fats and recovering a mixture of saturated and unsaturated fatty acids, fractionally distilling the mixture to recover a product containing but one saturated fatty acid, mixing the resultant mixture with a solvent, lowering the temperature of the solvent mixture ,to

- perature of the resultant product to crystallize the saturated fatty acids, and separating the solid phase from the liquid phase.

14. In a process for treating natural oils and fats containing unsaturated fatty acids and saturated fatty acids, the steps of hydrolyzing the oils and fats and recovering a mixture of saturated and unsaturated fatty acids, thesaturated fatty acids being present in the mixture in a proportion in excess of 10%, fractionally distilling the mixture to reduce the saturated fatty acid content to not substantially above 10%, mixing the-resultant mixture with a solvent, lowering the temperature to crystallize the saturated fatty acidsuand separating the solid phase from the liquid phase.

15. In a process for treating a mixture of unsaturated higher fatty acids and a plurality of Y saturated higher fatty acids, the saturated fatty crystallize the saturated acid, and then separating the solid phase from the liquid phase.

l2. In a process for treating natural oils and fats containing unsaturated fatty acids and saturated fatty acids, the steps of hydrolyzing the oils and fats and recovering a mixture of saturated and a plurality of unsaturated fatty acids. the saturated fatty acid being present in the mixture in a proportion in excess of 10%, fractionally distilling the mixture to reduce the number of saturated fatty acids and to reduce the saturated fatty acid contentto not substantially above 10%, mixing the resultant mixture with a solvent, lowering the temperature of'the mixture to crystallize the saturated fatty acids, and separating the solid phase from the liquid phase.

13. In a process for treating a mixture of unsaturated higher fatty acids and saturated higher fatty acids, the saturated fatty acids being present in the mixture in a proportion in excess of 10%, the steps of fraction-ally distilling the mixture to reduce the saturated fatty acid content to notsubstantially above 10%, mixing theresultant mixture with a solvent, lowering the temaoids being present in the mixture in a proportion in excess of 10%, the steps of fractionally distilling the mixture to reduce the number of saturated fatty acids and to reduce the saturated fatty acid content to not substantially above 10%, mixing the resultant mixture with a solvent, lowering the temperature to crystallize the saturated fatty acids, and separating the solid phase from the liquid phase.

16. In a process for treating a mixture of unsaturated higher fatty acids and saturated higher fatty acids, the saturated fatty acids being present in the mixture in a proportion in excess of 10% and including both 18 carbon atoms and acids having less than 18 carbon atoms, the steps of fractionally distilling the mixture to reduce the proportion of fatty acids having less than 18 carbon atoms to the remaining fatty aicds and toreduce the saturated fatty acid content to not substantially above 10%, mixing the resultant mixture with a solvent, lowering the temperatureof the resultant product to crystallize saturated fatty acids, and separating the solid phase from the liquid phase.

' EDWIN W. COLT.

REFERENCES CITED 1 The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Dec. 7, 1933 Number Number 

